In the past, a single screw compressor has been known which includes one screw rotor, a casing for containing the screw rotor, and two gate rotors as a compressor for compressing gas such as a refrigerant and air (see Japanese Patent Publication No. 2005-90293).
In this screw compressor, a compression chamber is formed by closed space partitioned by a helical groove of the screw rotor, the casing, and gates of the gate rotors. The screw compressor rotates the screw rotor, thereby moving the gates in the helical grooves of the screw rotor relatively to compress gas in the compression chamber. Furthermore, the casing is provided with a discharge port at a position corresponding to proximity of a terminating end of the helical groove of the screw rotor, and the helical groove is open in the discharge port as a result of the rotation of the screw rotor to thereby discharge compressed high-pressure gas from the discharge port.